A paint film-protecting sheet that provides a high level of weather resistance and minimizes staining of the paint film, and a substrate for such a sheet are provided. The paint film-protecting sheet has a pressure-sensitive adhesive (PSA) layer formed on a sheet-like substrate. The substrate has a surface resin layer (layer A) forming a surface of the substrate on the PSA layer side and one, two or more resin layers (layers B) superimposed on a back side of the layer A. The layer B contains an organic weathering stabilizer HMS having a weight-average molecular weight Mw of at least 1.5×10 3 in a predetermined amount Pb. The layer A is either free of the organic weathering stabilizer HMS or contains the stabilizer in a predetermined amount Pa which satisfies the condition Pa/Pb ‰¤ 0.5.
